Dehydration of hydroperoxides to ketones



United States Patent 3,291,834 DEHYDRATION 0F HY DROPEROXIDES T0 KETONES William J. Farrissey, Jr., Northford, C0nn., assignor, by

mesne assignments, to Esso Research and Engineering Company, a corporation of Delaware N0 Drawing. Filed Dec. 16, 1963, Ser. No. 330,599

Claims. (Cl. 260-586) The present invention is directed to the conversion of intermediate hydroperoxides to the corresponding ketones. More particularly, the invention is concerned with converting primary and secondary hydroperoxides of aliphatic and alicyclic unsaturated compounds to the corresponding unsaturated ketones. In its more specific aspects, the present invention is directed to the conversion of primary and secondary hydroperoxides to the corresponding unsaturated ketones by using an acid chloride and a nitrogen base.

The present invention may be brieflydescribed as a process for converting primary and secondary hydroperoxides of aliphatic and alicyclic unsaturated compounds having the following general formulae:

where R is hydrogen, a C to C alkyl or a C to C olefin and R is a C to C alkylene or a C to C olefin.

According to the methods used heretofore, aromatic and aliphatic hydroperoxides have been converted to the corresponding ketones by the dehydration of the hydroperoxide with strong bases. The dehydration of unsaturated hydroperoxides by bases, however, is not known since while the aromatic and aliphatic hydroperoxides and ketones are relatively stable in the presence of a base, the unsaturated hydroperoxides will readily polymerize. The use of acids, especially with the unsaturated hydroperoxides, is known to cause rearrangement.

According to the present invention, hydroperoxides are converted to the corresponding ketones by treating the hydroperoxides with a mixture of an acid chloride and a nitrogen base. The process is preferably carried out at a temperature within the range of about l0 to +10 C. but is kept as cool as possible to prevent a tarry product from forming. The reaction mixture should not be allowed to be warmed to a temperature in excess of 30 C. or the unsaturated ketones may not be recoverable.

The acid chlorides found suitable for the present invention are acetyl chloride, propionyl chloride, benzoyl chloride, and the like, but the preferred chloride is the acetyl chloride. The preferred nitrogen base in carrying out the present invention is pyridine, but other nitrogen bases, such as lutidine, collidine, and picoline, may be used.

The exact reaction which takes place in the conversion of the hydroperoxides to the corresponding ketones when mixed with an acid chloride and nitrogen base is complex and not fully known. However, a fuller appreciation of the present invention may be :had by the following proposed explanation. It is considered that the acid chloride reacts with the hydroperoxide to give the corresponding perester and hydrogen chloride. The presence of the nitrogen base, then, is essential to trap the hydrogen chloride as formed to prevent polymerization and formation of undesirable products by rearrangement. In fact, it is preferred that a large excess of nitrogen base be utilized in the conversion of the hydroperoxide to the corresponding ketone. It is then considered that the perester formed by the reaction of 3,291,834 Patented Dec. 13, 1966 the hydroperoxide with the acid chloride decomposes to the corresponding ketone and the acid corresponding to the acid chloride used. The organic acids formed, being weak acids, and also being in the presence of excess nitrogen base, do not cause the formation of undesirable products.

In carrying out the conversion process of the present invention, it is preferred to add the nitrogen base, such as pyridine, quickly to the hydroperoxide mixture while the acid chloride, such as the acetyl chloride, is slowly added thereto. It is pointed out that the terms quickly and slowly are used in the relative sense to point out that the excess nitrogen base may be added all at once to the hydroperoxide mixture while the best results are obtained if the addition of the acid chloride is extended over a period of about an hour or more. Although it is not the preferred method of converting th hydroperoxides, the acid chloride and nitrogen base may be first mixed in a common solvent and then to this mixture may be added slowly the primary and secondary hydroperoxide starting materials of the present invention. In the preferred method of handling the materials of the present invention, it is further desirable to use a common solvent for the acid chloride and nitrogen base, such as chloroform, benzene or methylene chloride. The term common solvent is used to define a material wherein the complex formed by the reaction of the acid chloride and the nitrogen base is soluble. While a solvent is not necessary in the preferred method, it is most desirable when the acid chloride and nitrogen base are first mixed.

According to the present invention, hydro-peroxides which may be formed in the air axidation of olefins can be converted to useful products. The chemical products formed are especially useful since the materials are maintained as unsaturated hydrocarbons without the materials being degraded or polymerized to unsuitable tarry products.

The present invention is further illustrated by the following examples which are set forth to merely illustrate and not to limit the present invention.

EXAMPLE I A solution of 21.66 g. of a crude mixture of cyclooctadiene hydroperoxides obtained by the air oxidation of cyclooctadiene and consisting of 3-hydroperoxy-l,5-cyclooctadiene and 6-hydroperoxy-1,4-cyclooctadiene in ml. of chloroform is cooled to 0 C. Sixty ml. of pyridine is added rapidly to this solution, and thereafter, 8.4 ml. of acetyl chloride in 10 ml. of chloroform is added slowly to the solution over 2.5 hours. The solution is-further stirred for 45 minutes at 0 C. and then allowed to warm to room temperature while stirring for another 2.25 hours. The product is poured in a separatory funnel, and the product is washed free of pyridine with 1 N HCl. The residual acid is washed free with water, and the product is dried in a solvent evaporator. A crude product (18.17 g.) is obtained which upon distillation yielded 9.6 ml. of ketones boiling at 6166 C. at 1.9 mm.. The-ketone product is a mixture of the following:

EXAMPLE II A solution of one gram of the hydroperoxides recovered from the air oxidation of 4-vinylcyclohexene and consisting of 4-hydroperoxy-4-vinylcyclohexene, 3-hydroperoxy- 4 vinylcyclohexene, 6-hydroperoxy-4-vinylcyclohexene;

and 6-hydroperoxy-3-vinylcyclohexene and 4 ml. of pyridine in 15 ml. of chloroform is treated with 1 ml. of acetyl chloride in chloroform solution at C. The solution is allowed to warm to room temperature and then heated for 3.5 hours at 55-60 C. on a water bath. The cooled reaction mixture is poured into water, the layers separated, and the chloroform phase washed free of pyridine with 1 N hydrochloric acid. After drying, the chloroform is evaporated to give 0.88 g. of an oil which on distillation gives a product which exhibits the characteristic NMR and IR spectra of vinylcyclohexenones. Further proof of structure shows the following ketones present:

EXAMPLE III In a 250 ml. round bottom flask are placed 4 g. of

cyclododecatrienyl hydroperoxide in 50 ml. of chloroform.

The solution is cooled to 0 C. with an ice bath and 12 ml. of dry pyridine is added. A solution of 1.7 ml. of acetyl chloride in 2 ml. of chloroform is then added slowly over 1.3 hours. The ice bath is removed and the reaction mixture stirred an additional 2 hours at room temperature. The reaction mixture is poured into a separatory funnel containing 20 ml. of 1 N hydrochloric acid solution. The chloroform solution is washed repeatedly with hydrochloricacid until no more pyridine remains. After sufficient water washing to remove all residual acid, the chloroform solution is dried with sodium sulfate and distilled. There is recovered about 3 g. of product which is approximately 50% ketone by NMR.

EXAMPLE 1V Ten millimoles of the hydroperoxide product obtained from the air oxidation of tri-isobutylene is dissolved in ml. of chloroform and the solution cooled to 0 C. Two m1. of picoline is then added followed by millimoles of benzoyl chloride added slowly over a 1-hour period. After warming to room temperature, the reaction mixture is washed with dilute hydrochloric acid solution and with water and the chloroform solution dried with sodium sulfate. Removal of the solvent gives about :a 65% yield of the mil-unsaturated ketone.

EXAMPLE V A solution of 1.1 g. (9.6 millimoles) of cyclohexenyl hydroperoxide in 10 ml. of chloroform and 1.8 g. of pyridine is treated with 1 ml. (14.1 millimoles) of acetyl chloride at 0 C. After the addition, the solution is allowed to warm to room temperature for 1 hour. The reaction mixture is washed with water, dilute hydrochloric acid, and again with water and dried with sodium sulfate. After evaporation of solvent, there remains 1.0 g. of a liquid which is approximately 65% ketone by NMR.

The nature and objects of the present invention having been completely described and illustrated and the best mode thereof set forth, What I wish to claim as new and useful and secure by Letters Patent is:

1. A method for converting an unsaturated hydroperoxide of the general formulae:

0 0H H(IJC=CH Where R is selected from the group consisting of a C to C al-kylene and a C to C olefin to the corresponding unsaturated ketone which comprises treating said hydroperoxide with a mixture of an acid chloride selected from the group consisting of acetyl chloride, propionyl chloride, and benzoyl chloride and a nitrogen base which will trap hydrogen chloride at a temperature less than 30 C washing free said nitrogen base from the reaction product with hydrochloric acid, and recovering said corresponding unsaturated ketone.

2. A method for converting an unsaturated hydroperoxide of the general formulae:

oon

where R is selected from the group consisting of a C to C alkylene and a C to C olefin to the corresponding unsaturated ketone which comprises mixing a nitrogen base which will trap hydrogen chloride to said hydroperoxide and slowly adding an acid chloride selected from the group consisting of acetyl chloride, propionyl chloride, and benzoyl chloride to the mixture at a temperature less than 30 C., washing free said nitrogen base from the reaction product with hydrochloric acid, and recovering said corresponding unstaturated ketone.

3. A method for converting an unsaturated hydroperoxide of the general formulae:

where R is selected from the group consisting of a C to C alkylene and a C to C olefin.

to the corresponding unsaturated ketone which comprises treating said hydroperoxide with a mixture of an acid chloride selected from the group consisting of acetyl chloride, propionyl chloride, and benzoyl chloride and a nitrogen base which will trap hydrogen chloride in a common solvent at a temperature less than 30 C., washing free said nitrogen base from the reaction product with hydrocholcric acid, and recovering said corresponding unsaturated ketone from the reaction product by evaporation of said solvent.

4. A method for converting a hydroperoxide selected from the group consisting of 3-hydroperoxy-1,5-cyclooctadiene and 6-hydroperoxy-1,4-cyclooctadiene to the corresponding unsaturated ketone which comprises forming a solution of said hydroperoxides in a common solvent, adding a nitrogent base which will trap hydrogen chloride to said solution, and thereafter adding an acid chloride selected from the group consisting of acetyl chloride, propionyl chloride, and benzoyl chloride while maintaing said solution at a temperature less than 30 C., washing free said nitrogen base from the reaction product with hydrochloric acid, and recovering said corresponding unsaturated ketone from the reaction product by evaporation of said solvent.

5. A method in accordance with claim 4 wherein said common solvent is chloroform, said nitrogen base is pyridine, and said acid chloride is acetyl chloride.

6. A method in accordance with claim 5 wherein the addition of said acetyl chloride is extended over a period of about one hour.

7. A method for converting a hydroperoxide selected from the group consisting of 3-hydroperoxy-4 vinylcyclohexene; 6-hydroperoxy-4-vinylcyclohexene; and 6-hydroperoxy-3-vinylcyclohexene to the corresponding unsaturated ketone which comprises forming a solution of said hydroperoxides in a common solvent, adding a nitrogen base which will trap hydrogen chloride to said solution, and thereafter adding an acid chloride selected from the group consisting of acetyl chloride, propionyl chloride, and benzoyl chloride while maintaining said solution at a temperature less than 30 C., washing free said nitrogen base from the reaction product with hydrochloric acid, and recovering said corresponding unsaturated ketone from the reaction product by evaporation of said solvent.

8. A method in accordance with claim 7 wherein said common solvent is chloroform, said nitrogen base is pyridine, and said acid chloride is acetyl chloride.

9. A method in accordance with claim 8 wherein the addition of said acetyl chloride is extended over a period of about one hour.

10. A method for converting the hydroperoxide product obtained from the air oxidation of triisobutylene to the corresponding a,;3-unsaturated ketone which comprises forming a solution of said hydroperoxide product in a common solvent, adding a nitrogen base which will trap hydrogen chloride to said solution, and thereafter adding an acid chloride selected from the group consisting of acetyl chloride, propionyl chloride, and benzoyl chloride 6 while maintaining said solution at a temperature less than 30 C., washing free said nitrogen base from the reaction product with hydrochloric acid, and recovering said corresponding unsaturated ketone from the reaction product by evaporation of said solvent.

References Cited by the Examiner Haw kins, Organic Peroxides, pp. 23 and 277 (1961). Tobolsky et al., Organic Peroxides, pp. 117 to 120 (1954).

LEON ZITVER, Primary Examiner.

M. JACOB, Assistant Examiner. 

1. A METHOD FOR CONVERTING AN UNSATURATED HYDROPEROXIDE OF THE GENERAL FORMULAE: 